During wear, contact lenses are susceptible to the accumulation of proteinaceous materials that may adhere to the surface of the lens. Proteinaceous materials include, for example, lysozyme, lactoferrin, albumin, and mucoproteins, all constituents of lachrimal tears. Contact lenses that are repeatedly worn over an extended period of time must be cleaned to remove these materials as part of a routine care regimen.
Particularly if contact lenses are not properly cleaned, lysozyme, mucoproteins, and the like can accumulate on the lenses and may lead to the lens wearer experiencing discomfort or a loss of visual acuity. The presence of proteinaceous deposits on the lens may also decrease gas permeability of the lenses or adversely affect the spectral characteristics of the lenses. Finally, proteinaceous deposits may interfere with the efficient sterilization of contact lenses.
Daily cleaning and/or disinfecting compositions or techniques now in predominant use on contact lenses do not prevent the accumulation of protein deposits over an extended period of time. In fact, one method of disinfecting, heat sterilization, may aggravate the problem by denaturing and precipitating proteinaceous materials onto the lens. Consequently, special cleaning compositions and techniques are in widespread use for removing the accumulation of protein deposits that cannot be adequately prevented by daily cleaning.
Accordingly, the cleaning of contact lenses is conventionally accomplished with one or both of two general classes of cleaners. Surfactant cleaners, generally known as "daily cleaners" because of their recommended daily use, are effective for the removal of most carbohydrate and lipid-derived matter. However, such cleaners are not as effective for removal of proteinaceous matter such as lysozyme. Typically, proteolytic enzymes derived from plant, animal, or microbial sources are used to remove the proteinaceous deposits. These "enzyme cleaners" are typically recommended for weekly use. Commonly, enzyme cleaners are employed by dissolving enzyme tablets in suitable aqueous solutions. See, for example, U.S. Pat. No. 5,096,607 to Mowrey-McKee et al. Other chemical agents that remove protein deposits have been developed. For example, U.S. Pat. No. 4,414,127 to Fu discloses compositions comprising metal chloride catalysts in combination with a peroxide that chemically degrade and remove proteinaceous deposits.
In addition to the use of proteolytic enzymes or other chemical agents that degrade protein, contact lens wearers may need to rub the contact lenses (typically between the forefinger and palm) during daily cleaning of contact lenses. This is usually required or recommended to retard the build-up of protein deposits that will eventually require an enzyme cleaner or other special cleaner for removing protein deposits.
Special cleaners and procedures for removing or degrading proteins are clearly an extra burden for contact-lens wearers, and the necessity for frequent "rubbing and cleaning" of contact lenses add to the time and effort involved in the daily care of contact lenses. Many contact lens wearers do not like the burden of having to perform a daily "rubbing and cleaning" regimen. Some wearers may even be negligent in the proper "rubbing and cleaning" regimen, which may result in contact-lens discomfort and other problems.
The deposition of proteinaceous materials can also cause adverse affects or limit the life of so-called planned replacement lenses (PRL) and disposable lenses that are designed to be used without enzyme cleaners and then discarded after a limited period of time. The build up of proteinaceous deposits may cause contact lens spoilage.
Another approach to solving the problem of protein deposits has been to try to prevent proteins from adhering to the contact lens surface in the first place. For example, U.S. Pat. No. 4,168,112 to Ellis discloses contact-lens solutions containing cationic polymers which are said to form a coating of a hydrophilic polyelectrolytic complex on the lens surface. This complex is alleged to act as a hydrogel "cushion" to increase the wettability and comfort of the lens. This complex is also said to increase the hydrophilic character of the lens and also reduce the tendency for mucoproteins to adhere to the lens surface. The examples in the patent are directed to rigid gas permeable (RGP) lenses. The patent discloses the use of polyquaternium polymers and copolymers generally, and exemplifies the immersion of a hard contact lens in a 0.1 solution of polyvinylbenzyl trimethyl ammonium chloride followed by a thorough rinse with distilled water.
Published PCT application WO 94/13774 to Powell et al. discloses a method for inhibiting the uptake of proteins by contacting a contact lens with a positively charged chemical agent having a molecular weight of 100 to 70,000. Such chemical agents include basic proteins and polypeptides such as protamine and polyarginine, both of which are said to have an average charge density greater than the average density of lysozyme, the most basic tear protein.
Missiroli et al. has found that bendazac lysine limits protein deposition on soft contacts lenses. See Missiroli, A. et al., CLAO Journal (Contact Lens Association of Ophthalmologists), 17(2), pp. 126-8 (April 1991). Bendazac lysine, an anti-cataract drug, is an oxyacetic acid.
The use of certain ionic polymers in contact-lens cleaning and preserving solutions is also known. For example, U.S. Pat. No. 5,096,607 and WO 94/13774 disclose the use of certain polyquaterniums as antimicrobial agents, typically in amounts less than 100 parts-per-million (ppm) in actual commercial practice. U.S. Pat. No. 4,443,429 to Smith et al. discloses the use in a contact-lens disinfecting solution of a dimethyldiallylammonium chloride homopolymer known as Merquat.RTM. 100 having a molecular weight of about 10,000 to about 1,000,000. While broad concentrations are recited in the patent, preferred concentrations are 0.0004 to about 0.02 weight percent (4 to 200 ppm). U.S. Pat. No. 4,388,229 to Fu discloses a contact-lens solution for rejuvenating lenses by removing adsorbed and occluded chemical and biological agents, particularly antimicrobial agents adsorbed from a disinfecting solution. The patent discloses the use of strongly basic anionic exchange resins having quaternary-ammonium exchange groups. After the rejuvenation procedure, the lenses may be treated with water or a cleaning and/or preserving solution to remove any residual rejuvenation solution.
Clearly, it would be desirable to be able to effectively prevent or inhibit deposition of proteins on the surface of contact lenses. It would be especially desirable to eliminate or minimize the need for special cleaning compositions or techniques to remove protein deposits from contact lenses. Finally, it would be highly desirable to eliminate or reduce the need for so-called "rubbing and cleaning." Preventing the deposition of proteinaceous materials on contact lenses in the first place would not only solve the above-mentioned problems associated with the accumulation of protein deposits, but would result in lens care becoming significantly more user-friendly and convenient. These are important attributes for many or most wearers of contact lenses.